FOCL

The FOCL system is an extension of the purely inductive FOIL.
FOIL generates each candidate specialization by adding a new literal to the preconditions.
FOCL generates additional specializations based on the domain theory. How?
We say that a literal is operational if it is allowed to be used in describing an output hypothesis.
At each point in the search FOCL adds candidates by
1. Considering each operational literal for the precondition.
2. Creating an operational and logically sufficient condition for the target concept according to the domain theory. Prune any unnecessary preconditions.